Robin could be another good one. He could act as a sort of big brother figure to the baby daughter. He could play with her, teach her some basic self - defense moves (in a very kid - friendly way), and help Batman keep an eye on her.
Maxine Gibson would be a great supporting character. Her tech - savvy skills could be crucial in helping Batman Beyond figure out how to combat Poison Ivy's new plant - tech hybrids. Another could be Commissioner Barbara Gordon. With her years of experience dealing with Batman and his rogues gallery, she can offer valuable advice to Terry. Also, Ace, the dog, could play an interesting role. Maybe he has some sort of special ability that can detect Poison Ivy's plants before they cause trouble.
Well, obviously Batman himself is a very important character. His presence, even if it's in the background sometimes, shapes the story as he is the father. Then there's the daughter herself. Depending on the fanfiction, she could have a name like Helena or something unique created by the author. Alfred is also often a popular character as he can act as a mentor or a source of wisdom for the daughter.
The Joker would be a classic choice. His chaotic and unpredictable nature would pose a great threat to Batman's daughter. He might try to corrupt her or use her as a pawn in his evil schemes against Batman.
Definitely the other firefighters at the firehouse. Casey, for example, could be a great support. He could offer Severide advice on being a father, based on his own experiences or just his general good - natured wisdom. Boden, as the chief, could also play an important role. He might be strict about work - life balance but also show a soft side when it comes to the impending arrival of the baby. And of course, the female firefighters could be there for Shay, like Gabby. They could have girl - talk about pregnancy and motherhood.
The Joker is a likely suspect. He loves to target Batman's loved ones to mess with him. He might use the kidnapping as a way to draw Batman into a twisted game, setting up elaborate traps along the way.
Their friends could be great supporting characters. For instance, their best friends could come over to help with the baby. They could bring gifts for the baby and give Josh and Gabi some much - needed breaks.
Klaus could be a great supporting character. He has a complex relationship with Rebekah, and his overprotective nature towards his family could extend to the baby. He might be a bit of a wild card, sometimes causing trouble but also being a powerful ally. Elijah is another good option. He's the more level - headed of the Mikaelson siblings, and his wisdom could be valuable in guiding Rebekah in raising the baby. Also, Hayley could be involved. Since she has her own experiences with having a baby in the supernatural world, she could offer practical advice and support to Rebekah.
Fez would be a great supporting character. He could provide some comical relief with his unique view on parenting and his eagerness to be involved. Kelso could also be good, as his somewhat clueless but well - meaning nature could add some interesting dynamics, like when he tries to give baby - related advice based on his own limited knowledge.
Hermione would be a great supporting character. She could be intrigued by Harry's strange behavior for a baby. She might try to study him like she does with her books, constantly observing and trying to figure out how he has such adult - like qualities. Their interactions would be interesting as Harry could offer her different perspectives on magic that she hadn't thought of before.
The iCarly crew could all be supporting characters in different ways. Spencer could be the cool uncle who builds amazing things for the baby. Tasha could be there to offer maternal wisdom to Carly. And the fans of iCarly in the fanfiction could also play a role, like helping out with a fundraiser for the baby's future education or something similar.